1. Field of the Invention
The present invention relates to a power conversion apparatus in which electronic components constituting a power conversion circuit and a cooler for cooling at least some of the electronic components are housed in its case.
2. Description of Related Art
An electric vehicle or a hybrid vehicle is equipped with a power conversion apparatus such as an inverter or a converter to convert source power into driving power for a drive motor. As shown in FIG. 35, such a power conversion apparatus 9 includes various electronic components including semiconductor modules 921 each incorporating therein switching elements, and a capacitor 922. For example, refer to Japanese patent Application Laid-Open No. 2009-159767. To prevent the temperature of the semiconductor modules 921 from increasing excessively, a cooler 93 is disposed in contact with the semiconductor modules 921.
The power conversion apparatus 9 further includes a control circuit board 96 on which a control circuit for controlling the semiconductor modules 921 is formed. The electronic components including the semiconductor modules 921, the cooler 93 and the control circuit board 96 are fixed to a case 94, and sealed within the case 94.
Accordingly, if the case 94 is not rigid enough, the electronic components and the control circuit board 96 fixed to the case 94 may vibrate considerably, causing wire breakage, or failure in the electronic components due to external force applied thereto.
When the power conversion apparatus 9 is located in an engine compartment of a vehicle, the case 94 may expand or contract considerably due to abrupt temperature change. In this case, since the components are fixed directly to the case 94, they may fail due to thermal stress applied to them.
The case 94 of the power conversion apparatus 9 is constituted of a case body 940, and bottom and top lids 941 and 942. Accordingly, the case 94 has two large sealing surfaces required to be water-tight. Accordingly, since the case 94 has to be provided with many sealing members, the power conversion apparatus 9 is disadvantageous in the manufacturing cost.
In addition, the maintainability of the power conversion apparatus 9 is not good enough in this case, because both the bottom lid 941 and the top lid 942 have to be removed for maintenance work. It might be possible that the case 94 has only one sealing surface, if the case 94 is constituted of a bottomed case body and a top lid. However, in this case, the maintainability and rigidity of the case 94 may become worse.
Further, since vibration of the electronic components directly fixed to the case 94 can transmit to a vehicle body through the case 94, unpleasant vibration sound may occur in the vehicle cabin. Conversely, since vibration of the engine can transmit to the electronic components and the control circuit board through the case 94, wire breakage or fault may occur.
Incidentally, to mount the power conversion apparatus on a vehicle, it is necessary to change its external shape on a vehicle type to vehicle type basis, because the position of connecting means of the power conversion apparatus for connection with external devices has to be adjusted depending on the shape and structure of a space (engine compartment, for example) in which the power conversion apparatus is disposed. Accordingly, the power conversion apparatus of the type in which the electronic components and the cooler are directly assembled to the case needs to be changed in its internal layout. This makes it difficult to improve the productivity, and to prevent reducing the manufacturing cost.